This invention relates generally to the field of drug delivery, and in particular to enhancing drug efficacy and reducing drug toxicity. More specifically, the invention relates to the drawing of blood into the thorax to increase vital organ perfusion to facilitate drug delivery.
Efficient drug delivery is critical factor in treating a variety of ailments. For example, drugs often need to be rapidly delivered to patients in cardiac arrest, or when suffering from diabetes, hypoglycemia, an anaphylactic reaction, seizures, asthma attacks, and the like. In some cases, drugs have short half lives and also need to be rapidly circulated. Hence, there is a need to rapidly distribute many drugs to the blood stream and vital organs. To increase the delivery rate of certain drugs, some have proposed simply increasing the concentration of the drug. However, the increased concentration may be toxic to the patient.
In one embodiment, the invention provides a method for administering a drug to a patient. The method is designed to increase the efficacy of the drug, and in some cases to reduce the toxicity of the drug. According to the method, a valve system is coupled to the patient""s airway. The valve system is configured to prevent or impede respiratory gases from flowing into the lungs for at least some time such that the intrathoracic pressure is artificially made to be less than atmospheric pressure. A drug is introduced into the patient, and the intrathoracic pressure is lowered in a repeating manner using the valve system to enhance blood to flow into the thorax. In this way, vital organ perfusion is increased to enhance the circulation of the drug. By increasing the circulation within the body with the valve system, the efficacy of the drug can be increased and less of the drug may be used to reduce the toxicity of the drug.
The method may be used to enhance drug efficacy and decrease toxicity for patients with low blood pressure, those in cardiac arrest, or those who need a rapid administration of a drug. For patients under cardiac arrest, the intrathoracic pressure may be reduced by using the valve system during standard CPR or by actively lifting the chest using a variety of CPR techniques, by electrically stimulating the respiratory and/or abdominal nerves or muscles, and the like while also preventing, restricting, or inhibiting respiratory gas flow into the lungs with the valve system for some period of time. The intrathoracic pressure may alternatively be reduced simply by breathing in while preventing or inhibiting respiratory gas flow to the lungs with the valve system. As another option, the intrathoracic pressure may be reduced by squeezing the chest and relaxing the chest with a chest caress while preventing or inhibiting airflow to the lungs with the valve system.
The valve system may be configured to prevent respiratory gases from entering the lungs until a certain threshold negative intrathoracic pressure is exceeded at which time gases may flow to the lungs. For example, the threshold negative pressure may be in the range from about 0 cm H2O to about 40 cm H2O. At this point, the valve system permits respiratory gases to flow into the lungs. The valve system may optionally have an attached valve to create a range of positive end expiration pressures (PEEP) that typically occurs during compression of the patient""s chest or when the patient exhales. This valve may be set to open when the positive intrathoracic pressure is in the range from about 0 cm H2O to about 20 cm H2O.
The drug may be administered using a variety of techniques, For example, the drug may be introduced intravenously, through the patient""s bone, through the patient""s airway, including orally, nasally, and endobrochially, rectally, transdermally, and the like. As another option, the drug may be administered through a facial mask that is coupled to the patient""s face or the valve system itself when coupled to the respiratory circuit.
A wide variety of drugs may be introduced into the patient. These include, for example, adrenaline or other supplemental drugs used to help maintain blood pressure when the patient is in cardiac arrest. Other examples include drugs that need to be rapidly delivered, such as glucose or adrenaline. Additional drugs include sodium bicarbonate, oxygen, steroids, vasopressor drugs, anti-arrhythmic drugs, anesthetics, anti-seizure medicines, and cooling solutions to cool the brain during cardiac arrest.